"Law & Order," NBC's classic crime procedural drama set in New York, has been cancelled after 20 seasons. One more season, and it would have earned the distinction of overtaking "Gunsmoke" as the longest-running series ever. Even though the series produced several spin-offs and will live on in syndication, fans are bereft and have even launched a Facebook campaign to bring it back. How did a straightforward cop show provoke so much loyalty?

It was an influential piece of historyAlthough it could be formulaic, "Law & Order" has earned its place in history, says Mary Schmich in the Chicago Tribune. It "left a social mark. It made prosecutors fashionable." It inspired "half the plots on TV," and gave a generation of actors their first starts. It's a "cultural milestone."

It was about the concept, not the stars' pulchritudeYou never saw any of this old-fashioned drama's stars on "those 'TV's hottest hotties' lists," says Ken Tucker ain Entertainment Weekly. It's one of the last shows where "the concept," not the casting, was the appeal. It was "never 'cool,'" but it "made a case for the decency — and flaws — of the justice system" and "gave us a lot of fine acting in the bargain." It's a shame it's gone.

It gave civil lawyers a good nameTort lawyers loved it, says Garett Epps in The Atlantic. Even though "no figure in American popular culture is more roundly reviled than the ambulance-chasing, injury-faking, fast-talking shyster shakedown artist," "Law & Order" portrayed the law as a "well-meaning guardian, not a blind machine." Very few mainstream dramas do that.

It showed the true face of New YorkUnlike the sanitized, one-dimensional city of "Friends" and "Sex and the City," says Melissa Rayworth in AP, the series "showed the world not just one New York but hundreds," from the "immigrant communities" to "middle-class families," from "Manhattan" to the "far boroughs." Produced by New Yorkers, the show "never trafficked in Gotham clichés" — and how many shows can we say that about?